Control system for automatic machines

ABSTRACT

Sequential operation of an automatic machine is controlled by an assembly of binary switches which are selectively operated by a selector member. Plunger operated microswitches may be used in conjunction with a selector member comprising a stiff apertured plate so that when the plate is pressed against an assembly of switches, it depresses the plungers except the ones located against the apertures and thus makes the selection. Leveroperated microswitches may alternatively be used in conjunction with a selector member having a profiled edge which is shaped to engage some levers and not others when it is brought into operational relationship with the switch array.

United States Patent [191 Collins July 24, 1973 [54] CONTROL SYSTEM FORAUTOMATIC 3,243,532 3/1966 De Bonduwe 200/46 IN 3,479,473 11/1969Rainstetter 200/46 3,515,339 6/1970 McEwan 235/6l.7

George Thomas Collins, Sutton Coldfield, England Assignee: BritishIndustries Plastics Limited,

Manchester, England Filed: June 10, 1971 Appl. No.: 151,853

Inventor:

Foreign Application Priority Data July 18, 1970 Great Britain 34,968/70US. Cl. 200/46, 235/61.7 Int. Cl. H01h 43/08 Field of Search 200/45, 46,47;

References Cited UNITED STATES PATENTS 2/1971 Mindell 200/46 11/1965Lutzen 200/46 Primary Examiner-Herman J. Hohauser Attorney-Cushman,Darby & Cushman 57 ABSTRACT Sequential operation of an automatic machineis controlled by an assembly of binary switches which are selectivelyoperated by a selector member. Plunger operated microswitches may beused in conjunction with a selector member comprising a stiff aperturedplate so that when the plate is pressed against an assembly of switches,it depresses the plungers except the ones located against the aperturesand thus makes the selection. Lever-operated microswitches mayalternatively be used in conjunction with a selector member having aprofiled edge which is shaped to engage some levers and not others whenit is brought into operational relationship with the switch array.

5 Claims, 7 Drawing Figures PATENTED 3.748.412

SHEET 1 OF 5 F g t! CONTROL SYSTEM FOR AUTOMATIC MACHINES This inventionrelates to the control of machines and is particularly concerned withthe operation of electrical systems for controlling automatic machinescapable of carrying out several different actions.

The operation of such a machine normally involves a number of individualactions which are carried out in a predetermined sequence. For example,the operation of a screw type injection moulding machine for mouldingthermoplastics or thermosetting materials involves the opening andclosing of mould halves, the plasticising of the material in the barrelof the machine, the rotary and reciprocatory movement of a feed screw,the heating and cooling of the barrel, the heating or cooling of themould, the cooling of the screw, the movement of the barrel, theejection of the moulded article, and so on, the mechanical operationsall in strict sequence. Not all of these individual actions are requiredin each case, or the sequence may vary, but the particular actions andthe sequence thereof for each individual material and each particularmoulding operation will be known in each case.

It is known to control machines such as injection moulding machineselectrically, and control systems are usually built up by first of alldetermining which particular actions the machine is required to performand in what sequence, and then constructing a circuit which will bringabout the performance of these actions in the required sequence. Suchcircuits may comprise normal electronic equipment, e.g., switchingblocks, timing blocks, filters, amplifiers and relays, etc. and theselection of the sequences of operation is achieved by the operation,usually manual, of some form of switching arrangement.

.The setting up of a sequence normally involves a number of individualselections being made to set the various selector switches, or pins in apeg board, to the positions which will provide the required sequence ofoperation. For example, to set a fully automatic sequence in aninjection moulding machine requiring core pulling, ejection, spruebreak, all of which can take place in a varying order in the sequence ofoperation, may involve setting six or more selector switches, most ofwhich have four possible settings. Errors can occur in making theselection and these can cause damage to costly moulds, and therefore theoperation of setting the sequences can only be carried out by qualifiedoperatives.

It is an object of the present invention to provide a control system fora machine, such as a moulding press, which enables the machine to carryout a desired sequence of a plurality of actions and which can bemodified simply and quickly by an unskilled operative with reliabilityand safety.

According to the present invention, selection means for the controlsystem of an automatic machine comprises a plurality of binary switchesarranged to operate the various functions of the machine and a selectormember which co-operates with said binary switches and is adapted tooperate such of the binary switches as are necessary to achieve adesired selection and/or sequence of the said functions.

The invention also provides an automatic machine having a sequentialcontrol system comprising such selection means.

Thus a machine will be provided with a set of selector members, each ofwhich is adapted to operate the requisite binary switches to achieve oneparticular sequence or selection.

Conventional on-off microswitches are very suitable for use in ourinvention, being so connected into the machine circuit that theselection is made by some microswitches being depressed and some not.The selector member engages the array of microswitches to operate someof them and thus make the selection. Encapsulated switches areespecially suitable for use in moist or dusty environment givingenhanced reliability.

In one form of construction, the microswitches are lever-operated andthe selector member takes the form of a card wilh a shaped profile. Themicroswitches may be mounted in a row so that their operating levers arein line with two slots running at sides of a rack on which the switchesare mounted. When a card is inserted into the slots and pushed into therack beneath the levers of the microswitches selected switches areoperated. The leading edge of the card profiled for a particularsequence has areas which are not cut away so that when the card isinserted into the rack the microswitch levers in these areas aredepressed and the switches are thus actuated. Where it is required thatthe card should not actuate a switch, the area of the card which wouldcome in contact with the lever is cut away. The selection of whichswitches will be operated when the card is inserted is therefore decidedby the profile of the leading edge of the card.

In a preferred construction, the microswitches are plunger operated andare arranged with the plungers in a plane. The selector member then maytake the form of a card or stiff plate provided with a number ofapertures and arranged to be held in contact with the switch array todepress the plungers of all the microswitches except the ones locatedagainst the apertures. Thus, with these arrangements the card may beapplied to the microswitch array by an unskilled operative, thusactuating the desired microswitches to make the selection. A set ofcards provides for the selections of standard sequences and a cardgiving the correct sequence, say for a particular mould being installedin the machine is issued with the other instructions for operating themould.

The microswitches can be placed in various positions in the .rack sothat they are actuated by the card when it is inserted. The card can beinserted above or below the microswitches according to whether themicroswitch levers or plungers are positioned above or below the body ofthe microswitch.

One preferred embodiment of the invention will now be described by wayof example'with reference to the accompanying drawings in which:

FIG. 1 schematically illustrates an injection moulding machine,

FIG. 2 is a perspective view of a control console for this machine,

FIG. 3 is a circuit diagram illustrating part of the control circuitscontrolled by a sequence selector,

FIGS. 4, 5 and 6 are circuit diagrams of printed circuit cardsincorporated in the circuit of FIG. 3, and

FIG. 7 is a perspective view on a larger scale of the sequence selectorunit fitted in the control console of FIG. 2 and included in the circuitof FIG. 3.

The injection moulding machine as shown in FIG. I may be used formoulding plastics materials in a mould having, for example, separabledies. Plastics material is contained in a hopper 11 which feeds a heatedscrew injection cylinder 12 having an outlet nozzle 13. The screw 12 isdriven by hydraulic motors (not shown). An assembly 14 houses aseparable mould, one part carried on a fixed platen with an inletcooperating with the injection nozzle 13, and the other part carried ona reciprocable hydraulic ram operated platen. Manual controls 15 andindicators 16 are shown at the front of the injection moulding machine,and a compartment 17 houses solenoid valves controlling variousoperations in the injection moulding process.

The injection moulding machine requires only brief description as itsconstruction and operation will be known to those skilled in the art.

A control console is shown in FIG. 2 which generally comprises injectioncylinder temperature controllers having dials 18, sequence selector unit19, digital setting timers 20, settable time delay controls 21 and arack 22 housing in parallel vertical alignment a plurality of printedcircuit boards or cards 23.

The printed circuit cards 23 are removably located in the rack 22 bymeans of edge connectors. Each printed circuit card 23 contains thenecessary circuit components, for example, filters, logical elements,resistors and capacitors, amplifiers, and the like, for controlling aparticular function or operation in a sequence of steps forming aninjection moulding process. For example, one card controls the movementof the mould halves, another card controls the injection feed screw, athird card controls the ejection of a moulded article, and on. Ifdesired, more than one action may be controlled by a single card. Forexample, both the opening and the closing movements of the mould halvesmay be controlled by a single card. FIG. 3 shows part of the controlcircuit which controls the ejection system of the machine, and itincludes three of the printed circuit cards 23, the circuits of whichare respectively shown in FIGS. 4, and 6. The cards 4, 5 and 6 controlvarious actions which it is desired that the injection moulding machineof FIG. 1 shall perform. Circuit card 4 controls the operation of theejection system, circuit card 5 controls the ejection sequences andcircuit card 6 controls the operation of the dies.

Each circuit on a printed circuit card causes solenoid valves orpneumatic valves to control hydraulic valves operating the injectionmoulding machine, allowing particular sequences to operate with requiredtiming. Certain variations in the control of the injection mouldingmachine may be effected by temperature controllers (of which the dials18 are illustrated), digital setting timers 20, and the settable timedelays 21 shown in the console illustrated in FIG 2. The constructionand operation of such controls will be known to those skilled in theart.

It will be appreciated that the main control console for the machinewill be wired for all possible actions which the machine may be requiredto perform. The control system of the invention simply selects which ofall possible actions are to be performed in any one case and the orderand timing of the actions.

The circuit of FIG. 3, in addition to circuit cards 4, 5, 6 includessolenoid operated valves 24, 25, 26, 27, located on the machine andrespectively controlling ejectors, stripper, clamp and clamp pressurecut-off. Also located in appropriate places on the machine are variouslimit switches (MS) operated by movement or pressure to control thefollowing functions:- core extraction (MS 11), core insertion (MS 12),ejectors return (MS 14), ejectors forward (MS 17), stripper out (MS 19),safety gate interlock (MS 20) and stripper in (MS 22). The circuitincludes a series of selector microswitches SS 3, SS 7, SS 11, SS 17, SS21, SS 22, SS 23, SS 29, SS 35, SS 36 and SS 37 and is completed bytimer contacts 28 and press button manual ejector switch 29. Each ofcircuit cards 4, S, 6 shown in FIGS. 4, 5, 6 respectively includefilters 30, NOR logical elements 31, resistances 32 and power amplifiers33. The card of FIG. 4 controls the operation of the ejectors and isconnected into the circuit of FIG. 3 by terminals 404, 406, 410, 411,412, 413, 417, 418 and 423. The card of FIG. 5 controls ejectionsequences and the operation of the stripper and is connected into thecircuit of FIG. 4 by terminals 506, 508, 510, 511, 512, 513, 515, 517and 523, and also includes diode 34. The card of FIG. 6 controls theoperation of the dies and is connected into the circuit of FIG. 3 613,terminals 605, 606, 607, 608, 609, 610, 611, 612, 6138 621 and 623.

The sequence selector unit shown in FIG. 7 comprises a plurality ofmicroswitches (SS) each having an operating plunger 35 located towardsone end. The microswitches are arranged in rows with the plungers 35staggered alternately. The microswitches SS are mounted in a box 36having a hinged lid 37 fitted with a catch 38. A plate 39 is mountedinside the lid 37 to carry four compression springs 40. The box 36 isadapted to receive a stiff key-plate 41 formed with apertures 42 whichare each dimensioned so as to allow free passage of the plunger 35 of amicroswitch SS. Three guide-holes 43 formed in the key-plate 41 aredimensioned and arranged to engage with three pins 44 in box 36, thusensuring that the key-plate 41 can only be inserted in box 36 in itscorrect disposition. When key-plate 41 is placed in the box 36, the lid37 closed and the catch 38 engaged, the springs 40 urge the keyplate 41towards the microswitches SS to depress all the plungers 35 which arenot located beneath any of the apertures 42. Thus the mannerin which theapertures 42 are arranged in the key-plate 41 determines whichmicroswitches are actuated and which are not and thus controls theselection of the sequence of operation of the machine.

FIG. 7 shows a key-plate 41 having a large number of holes 42 wherebyonly a minor proportion of the mircoswitches SS are actuated bydepression of the plungers 35 when the key-plate 41 is inserted. It ispreferred, however, to arrange the microswitches SS so that the circuitis closed when the plunger is not depressed, i.e., when a hole isprovided in the key-plate to allow free passage of the plunger. Thisminimises the number of holes which must be cut to achieve a particularsequence of operation.

For example, if a key-plate is formed with holes so that the plungers ofswitches SS 7, SS 11 and SS 23 are not depressed, then the machineoperates so that the ejectors go forward, operate and returnimmediately. If a key-plate is formed with holes so that the plungers ofswitches SS 7, SS 11, SS 23 and SS 29 are not depressed, then theejectors move forward, back and then forward again for a secondejection. If a key card is formed with holes so that the plungers ofswitches SS 1 1, SS 17 SS 23 and SS 35 are not depressed, then strippersare also brought into play and in operation the ejectors move forwardfollowed by the strippers, then the ejectors move back, again followedby the strippers.

This describes that part of the operation of an injection mouldingmachine concerning ejection, but the other operations of the machine,such as injection, core pulling, sprue break, closing, opening and othermovements of the die, control of pressure, etc., together with safetyinterlocks can be controlled in the same way, using sequence circuitswhich are selected by the operation or non-operation of microswitches Swhen covered by a key-plate 41.

Although the invention has here been described in its application to theautomatic control of an injection moulding machine, it can clearly beused in any automatic machine using selector switches to carry out adesired selection and/or sequence of a plurality of actions.

What is claimed is:

1. In combination with an automatic moulding machine, a control systemcomprising:

a plurality of electronic timing and function control means forautomatically controlling the duration and operational characteristicsof a corresponding plurality of particular functions in a sequence ofsteps used in a moulding process,

a plurality of binary switches electrically connected to operaterespectively corresponding ones of said control means, and

a removable selection member which when fully and fixedly inserted inplace, cooperates with said binary switches to cause actuation ofpredetermined ones of said binary switches to thereby achieve a desiredpredetermined set of functions for a particular moulding process, thesaid selection member remaining in place to maintain said actuation ofsaid switches during the entire moulding process.

2. Apparatus as in claim 1, wherein:

said binary switches comprise microswitches arranged in an array, and

said selector member is adapted to engage in the array of microswitcheswhereby some of the microswitches are operated and some are not operatedthus effecting a selection of operations.

3. Apparatus as in claim 2, wherein:

the microswitches are lever-operated, and

the selector member is a card having a shaped profile.

4. Apparatus as in claim 2, wherein:

the microswitches are lever-operated and are mounted in a row with theiroperating levers in line, and

the selector member is a card having a shaped profile held in two slotsso that its leading edge passes through the operating plane of thelevers,

the shaped profile being formed by cutting away parts of the leadingedge so that it does not engage the levers of the switches which are notintended to be actuated.

5. Apparatus as in claim 2, wherein:

the microswitches are plunger-operated and arranged with the plungers inone plane, and

the selector member is a stiff plate provided with a number of aperturesand arranged to be urged into contact with the switch array to depressthe plungers of all the microswitches except the ones located againstthe apertures.

1. In combination with an automatic moulding machine, a control systemcomprising: a plurality of elEctronic timing and function control meansfor automatically controlling the duration and operationalcharacteristics of a corresponding plurality of particular functions ina sequence of steps used in a moulding process, a plurality of binaryswitches electrically connected to operate respectively correspondingones of said control means, and a removable selection member which whenfully and fixedly inserted in place, cooperates with said binaryswitches to cause actuation of predetermined ones of said binaryswitches to thereby achieve a desired predetermined set of functions fora particular moulding process, the said selection member remaining inplace to maintain said actuation of said switches during the entiremoulding process.
 2. Apparatus as in claim 1, wherein: said binaryswitches comprise microswitches arranged in an array, and said selectormember is adapted to engage in the array of microswitches whereby someof the microswitches are operated and some are not operated thuseffecting a selection of operations.
 3. Apparatus as in claim 2,wherein: the microswitches are lever-operated, and the selector memberis a card having a shaped profile.
 4. Apparatus as in claim 2, wherein:the microswitches are lever-operated and are mounted in a row with theiroperating levers in line, and the selector member is a card having ashaped profile held in two slots so that its leading edge passes throughthe operating plane of the levers, the shaped profile being formed bycutting away parts of the leading edge so that it does not engage thelevers of the switches which are not intended to be actuated. 5.Apparatus as in claim 2, wherein: the microswitches are plunger-operatedand arranged with the plungers in one plane, and the selector member isa stiff plate provided with a number of apertures and arranged to beurged into contact with the switch array to depress the plungers of allthe microswitches except the ones located against the apertures.